1. Field of the Invention
An optical connection structure which permits connection between an optical fiber and an optical waveguide without centering, and a production method of an optical waveguide to be used for the optical connection structure are disclosed.
2. Description of the Related Art
Optical fibers are generally used for optical communications and the like for transmitting optical signals for relatively long distances. An optical waveguide is used for connection between the optical fibers and for transmission of the signals for relatively short distances. In order to facilitate alignment between the optical axes of the optical fibers and the optical axes of the optical waveguide (or to obviate a centering operation) for the optical connection, it is a conventional practice to provide optical fiber fixing grooves coaxially with cores of the optical waveguide in a substrate formed with the optical waveguide, and fit the optical fibers in the grooves for positioning and fixing the optical fibers.
The optical fiber fixing grooves are provided in a longitudinal end portion of the optical waveguide (in areas of the longitudinal end portion extending along extension lines of the cores and not formed with the cores). The grooves are typically elongated grooves each having a V- or U-shaped cross section, and one-side ends of the grooves are open in a longitudinal end face of the optical waveguide to communicate with the outside.
Exemplary methods for forming the optical fiber fixing grooves include a method such that grooves are preliminarily formed in a substrate serving as a base to be formed with an optical waveguide by etching, embossing or machining (e.g., cutting) (see, for example, JP-A-HEI8(1996)-313756 and JP-A-2001-350051), and a method such that core-containing parts of an end portion of an optical waveguide formed on a substrate are cut off by dicing or by irradiation with a laser beam to form grooves and expose ends (end faces) of the cores (see, for example, JP-A-2000-105324).
However, a structure obtained by preliminarily forming the optical fiber fixing grooves in the base substrate to be formed with the optical waveguide suffers from lower dimensional and positional accuracy of the grooves due to limitation in the accuracy of the etching process and the machining process. Since the optical waveguide is formed on the substrate after the formation of the grooves, it is difficult to properly position the optical waveguide cores with respect to the optical fiber fixing grooves. This often requires an additional process for cutting an end portion of the optical waveguide to expose the ends of the cores, so that processing errors are liable to be gradually accumulated. As a result, the optical axes of the optical fibers (optical fiber cores) are not accurately aligned with the optical axes of the optical waveguide cores.
A structure obtained by forming the grooves by cutting off the core-containing parts of the end portion of the optical waveguide formed on the substrate by dicing or the like also suffers from lower dimensional and positional accuracy due to limitation in the accuracy of the machining process. Where the formation of the grooves is achieved by utilizing the laser beam, the laser processing accuracy is higher than the aforementioned machining accuracy. However, the characteristic properties of the optical waveguide are liable to be degraded due to heating with the laser beam, and dust is liable to remain after the laser processing.
An optical connection structure is provided which permits easy and automatic alignment between the optical axes of the optical fibers and the optical axes of the optical waveguide cores. An optical waveguide production method is also provided which ensures that an optical waveguide to be used for the optical connection structure can be efficiently produced with higher dimensional accuracy.